Catheters are used for insertion into a blood vessel or a body cavity to bring a catheter distal end to a target site and performing injection of a medicine for therapy or a radiopaque material for diagnosis (as a disclosure of an exemplary conventional catheter, refer to U.S. Pat. No. 6,068,622).
In the case where a catheter is percutaneously inserted into a blood vessel, for example, the catheter is inserted and passed in a sheath introducer which is preliminarily made to puncture the blood vessel through a skin. In this case, in order to maintain the distal end position of the catheter at an arbitrary position, it is desirable that the position of the catheter relative to the sheath introducer can be fixed and that the fixing position can be changed to an arbitrary position.
In the case of a catheter in which the distal end of the shaft is comparatively hard, the catheter may be used as an outer catheter, and an inner catheter having a flexible distal end may be inserted and passed in the lumen of the outer catheter. In such a situation, by advancing the catheters in the blood vessel with the distal end of the inner catheter kept protruding from the distal end of the outer catheter, the blood vessel wall can be prevented from being damaged. In this case, it is desirable that the length of projection of the distal end of the inner catheter from the distal end of the outer catheter can be kept constant, and can be changed to an arbitrary position.